From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B28E2C4167B for ; Tue, 5 Dec 2023 13:45:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345477AbjLENoy (ORCPT ); Tue, 5 Dec 2023 08:44:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52392 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345584AbjLENks (ORCPT ); Tue, 5 Dec 2023 08:40:48 -0500 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9E627199 for ; Tue, 5 Dec 2023 05:40:53 -0800 (PST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id EB08A139F; Tue, 5 Dec 2023 05:41:39 -0800 (PST) Received: from [10.57.73.130] (unknown [10.57.73.130]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AA65A3F5A1; Tue, 5 Dec 2023 05:40:51 -0800 (PST) Message-ID: <183cf38c-476e-44c4-a8c7-22ed43122b41@arm.com> Date: Tue, 5 Dec 2023 13:40:51 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 34/39] mm/rmap: introduce folio_try_dup_anon_rmap_[pte|ptes|pmd]() Content-Language: en-GB To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , "Matthew Wilcox (Oracle)" , Hugh Dickins , Yin Fengwei , Mike Kravetz , Muchun Song , Peter Xu References: <20231204142146.91437-1-david@redhat.com> <20231204142146.91437-35-david@redhat.com> <88a341bf-0b6a-454a-aeb1-0699233eb37c@redhat.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/12/2023 13:32, David Hildenbrand wrote: > On 05.12.23 14:17, David Hildenbrand wrote: >> On 05.12.23 14:12, Ryan Roberts wrote: >>> On 04/12/2023 14:21, David Hildenbrand wrote: >>>> The last user of page_needs_cow_for_dma() and __page_dup_rmap() are gone, >>>> remove them. >>>> >>>> Add folio_try_dup_anon_rmap_ptes() right away, we want to perform rmap >>>> baching during fork() soon. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>>    include/linux/mm.h   |   6 -- >>>>    include/linux/rmap.h | 145 +++++++++++++++++++++++++++++-------------- >>>>    2 files changed, 100 insertions(+), 51 deletions(-) >>>> >>>> diff --git a/include/linux/mm.h b/include/linux/mm.h >>>> index 24c1c7c5a99c0..f7565b35ae931 100644 >>>> --- a/include/linux/mm.h >>>> +++ b/include/linux/mm.h >>>> @@ -1964,12 +1964,6 @@ static inline bool folio_needs_cow_for_dma(struct >>>> vm_area_struct *vma, >>>>        return folio_maybe_dma_pinned(folio); >>>>    } >>>>    -static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma, >>>> -                      struct page *page) >>>> -{ >>>> -    return folio_needs_cow_for_dma(vma, page_folio(page)); >>>> -} >>>> - >>>>    /** >>>>     * is_zero_page - Query if a page is a zero page >>>>     * @page: The page to query >>>> diff --git a/include/linux/rmap.h b/include/linux/rmap.h >>>> index 21d72cc602adc..84439f7720c62 100644 >>>> --- a/include/linux/rmap.h >>>> +++ b/include/linux/rmap.h >>>> @@ -354,68 +354,123 @@ static inline void folio_dup_file_rmap_pmd(struct >>>> folio *folio, >>>>    #endif >>>>    } >>>>    -static inline void __page_dup_rmap(struct page *page, bool compound) >>>> +static inline int __folio_try_dup_anon_rmap(struct folio *folio, >>> >>> __always_inline? >> >> Yes. >> >>> >>>> +        struct page *page, unsigned int nr_pages, >>>> +        struct vm_area_struct *src_vma, enum rmap_mode mode) >>>>    { >>>> -    VM_WARN_ON(folio_test_hugetlb(page_folio(page))); >>>> +    int i; >>>>    -    if (compound) { >>>> -        struct folio *folio = (struct folio *)page; >>>> +    VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); >>>>    -        VM_BUG_ON_PAGE(compound && !PageHead(page), page); >>>> -        atomic_inc(&folio->_entire_mapcount); >>>> -    } else { >>>> -        atomic_inc(&page->_mapcount); >>>> +    /* >>>> +     * No need to check+clear for already shared PTEs/PMDs of the folio. >>>> +     * This includes PTE mappings of (order-0) KSM folios. >>>> +     */ >>>> +    if (likely(mode == RMAP_MODE_PTE)) { >>> >>> Presumbly if __always_inline then the compiler will remove this if/else and just >>> keep the part indicated by mode? In which case "likely" is pretty useless? Same >>> for all similar sites in the other patches. >> >> Yes, also had this in mind. As long as we use __always_inline it >> shouldn't ever matter. > > It seems to be cleanest to just do: > > switch (mode) { > case RMAP_MODE_PTE: >     ... >     break; > case RMAP_MODE_PMD: >     ... >     break; > } > Agreed.